RenderLens — Technical-SEO audit for JS-heavy sites & live news

About

🔎 RenderLens — The Technical-SEO X-Ray for JavaScript-Heavy Sites

Every modern page has two faces. The raw HTML the server sends. The rendered DOM after JavaScript finishes. Users see one. Googlebot's first crawl sees the other. Bingbot, social preview crawlers, RSS readers, AI scrapers — all different. That gap is where ranking equity quietly leaks.

RenderLens freezes BOTH frames and runs them through a 14-panel audit.

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✨ WHAT YOU GET

📊  World-class diff engine
Line-by-line, word-by-word, syntax-highlighted. Collapsible unchanged ranges, sticky before/after column headers, change-density minimap, next/previous change keyboard navigation, full-text search, side-by-side and unified views. The diff tool you'd expect from a dedicated diff tool — but for HTML specifically.

🔍  SEO auditor, severity-scored
🔴 Critical · 🟡 Warning · 🔵 Info findings for:
   → noindex splits
   → JS-injected canonicals
   → JS-only H1s and navigation
   → schema visible only after render
   → alt-text regressions
   → cache lag
   → and more
Per-row diff tables for headings, links, images, body copy, meta, and resources — every one exports to CSV.

📰  Live Blog auditor (v1.4.3)
Built for newsrooms covering breaking news and live sports.

   🏆  Top Stories eligibility card — 5-point score, green/red bullets, tells you exactly why you're in or out
   🕷️  Per-crawler visibility matrix — what Googlebot first-wave, Googlebot WRS, Bingbot, social crawlers, and RSS/AI scrapers each see, with exact update counts per crawler
   🚨  Cache / SSE lag detector — newest post timestamp in raw vs rendered, color-coded 🟢🟡🔴
   🧠  "Why was the last crawl stale?" root-cause card — parses CDN and framework cache headers on every refetch, then explains in plain English which layer is causing the lag (CDN HIT, ISR STALE, SSE-only, origin no-cache, etc.) with a specific copy-paste fix recipe
   ♻️  Real-time auto-refresh (on by default, 15 s) — leave the diff view open during a match, new posts flash green as they land
   🛠️  Severity-scored fix cards with exact Cache-Control headers, surrogate-key purge snippets, revalidate values, CDN-worker recipes

🕵️  Tracker detection
Category-level classifier — analytics, advertising, session-replay, consent, and error-tracking scripts — with a dedicated "injected by JavaScript" flag.

🎨  Visual compare
Full-page sandboxed iframes of both HTMLs side by side, with synced scroll and mobile viewport presets (375 / 768 / 1024 / 1440).

🤖  User-agent override
Capture the page as Googlebot (mobile & desktop), Bingbot, iPhone, Android, or iPad. See what that crawler really receives.

🧰  DevTools panel
A dedicated RenderLens tab inside Chrome DevTools, scoped to the inspected page.

📄  Shareable HTML report
One click → a self-contained .html file with every KPI, the full diff, all tables, and both source trees. Attach to Jira, Slack, Linear. Opens on any browser, needs nothing else.

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🎯 14 PANELS

Summary · Side-by-side · Unified · 🖼️ Visual · 🔍 SEO · 📰 Live Blog · 🕵️ Trackers · Elements · Attributes · Resources · 🎨 Styles · 🔬 Inspect · Raw · Rendered

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⌨️ KEYBOARD FIRST

Ctrl/Cmd+Shift+L  — capture active tab
Ctrl/Cmd+Shift+R  — open popup
1–9, 0            — switch tabs
n / p             — next / previous change
/                 — focus search
h                 — hide unchanged
w                 — toggle word-level diff
?                 — cheatsheet

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👥 BUILT FOR

🧠  SEO teams auditing how rendering and non-rendering crawlers see JavaScript-heavy sites
📰  Newsroom engineers shipping live blogs that need Top Stories the second they go live
🐞  Frontend engineers hunting hydration and server/client-mismatch bugs
🕵️  Compliance reviewers auditing post-load script injection
⚡  Performance engineers quantifying server-shipped vs client-grown markup

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🔐 100% LOCAL. ZERO TELEMETRY.

No analytics. No remote calls beyond the explicit raw-HTML refetch of the URL you asked to capture. Session storage is scoped to the tab and discarded when the tab closes. Open source, MIT licensed.

Built with caffeine and curiosity in India.